Vehicle information and entertainment systems and consumer entertainment devices may employ sophisticated graphical schemes. A vehicle information and entertainment system may for instance display both safety relevant, such as the vehicle speed and engine temperature, and non-safety relevant information, such as video or navigation information at the same time. For example, U.S. Pat. No. 5,784,036 discloses a display device for creating a display image in front of a vehicle's windshield. The display device includes a display controller which controls a display to show safety relevant information, such as vehicle speed and not safety relevant information such as audio system control switches, telephone control switches.
However, a disadvantage of this prior art system is that the display controller may generate a wrong image, for example due to a fault in the hardware or software of the display controller, which may result in a dangerous action of the person looking at the display image in front of a vehicle's windshield in case the faulty parts of the display image contain safety relevant information.